1. Field of Invention
The invention relates to a driving apparatus for automobiles and, more particularly, to a hydraulic pressure generating device for the supply of hydraulic pressure in an apparatus for driving an electric vehicle or a hybrid driving apparatus.
2. Description of Related Art
An apparatus for driving an electric vehicle and a hybrid driving apparatus are known as apparatuses for driving automobiles that use an electric motor (including a generator used as an electric motor in this specification) as a driving source. Since the electric motor is subjected to use under sharp fluctuations in load in such a driving apparatus, the driving apparatus must be provided with a hydraulic pressure generating device and a hydraulic circuit to not only lubricate different mechanical components of the driving apparatus, but also to cool the electric motor under heavy loads and, moreover, to lubricate a gear train if it is included therein for power transmission, and control engagement of a friction device if one is included therein.
An example of a known hydraulic pressure generating device is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. HEI 10-89446. Disclosed in this publication is a hydraulic pressure generating device (20; a reference numeral assigned for drawings in the corresponding publication; the same applies to figures in parentheses hereunder) that is connected, through two one-way clutches (36, 38), to a carrier shaft (127) coupled to an engine (150) and a ring gear shaft (126) coupled to a motor (MG2) and that supplies a planetary gear (120) and other components with a lubricating oil.
An example of a known hydraulic circuit, in which an oil pump (51) driven by an engine (11) is used as a hydraulic pressure generating device, is disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-53603. This hydraulic circuit is provided with a first oil passage (A) through which an oil pressure having a required line pressure is introduced to a brake (28). It is further provided with, as a sixth oil passage (F), an oil passage for a lubricating system through which the oil pressure is sent to different parts of a driving system comprising power drive transmission elements, such as a countershaft (31) and a differential device (36), and, as a seventh oil passage (G), an oil passage for a cooling system through which a cooling oil is sent to a generator (16) and a driving motor (25).
The hydraulic pressure generating device (20) disclosed in the above-mentioned Publication No. HEI 10-89446 is formed integrally with a case (147) on an end portion opposite to the engine (150), which presents a disposition problem in terms of an axial length of a power output device becoming extremely long. In terms of a configuration for oil passages, too, the length of an oil passage for the supply of oil pressure to the planetary gear (120) becomes long in conjunction with the above disposition problem. This makes the structure of oil passages in the case (147) complicated, which increases the number of man-hours and cost expended in machining. It also increases oil passage resistance, presenting problems of an increased amount of power loss and oil leak in the hydraulic pressure generating device (20).
Such problems involved in the oil passage structure become particularly conspicuous in a case, in which the oil pressure from the oil pump (51), used as the hydraulic pressure generating device, is supplied to a plurality of locations (brakes, parts of a driving system, and an electric motor) for use in a plurality of purposes (servo pressure control, lubrication, and cooling), as in the art disclosed in the above-mentioned Publication No. HEI 9-53603. It is therefore necessary to dispose the hydraulic pressure generating device in an optimum position, at which the size of the driving apparatus is not affected and, at the same time, the lengths of oil passages to different locations are kept short.
The invention thus provides a driving apparatus, in which a hydraulic pressure generating device is disposed as efficiently as possible in an internal space thereof from viewpoints of both its own disposition position as well as a configuration of associated oil passages.
To achieve the foregoing, a driving apparatus according to the invention is provided with an electric motor and a differential device that are disposed in a mutually parallel axial relationship, a gear train that operatively couples the electric motor and the differential device by means of a parallel shaft, and a hydraulic pressure generating device. The driving apparatus is characterized in that, in the gear train that comprises a counter drive gear disposed on an axis of the electric motor, a counter driven gear is disposed on a countershaft that runs parallel with the axis of the electric motor and engaged with the counter drive gear, and a differential drive pinion gear is disposed on the countershaft and engaged with a differential ring gear disposed on an axis of the differential device, with the hydraulic pressure generating device disposed in a clearance space created between each of the two adjacent gears of the gear train with the gear train viewed in an axial direction.
In the construction according to a first exemplary aspect of the invention, the hydraulic pressure generating device is disposed in a clearance space created between each of the two adjacent gears of the gear train, which makes it possible to dispose the hydraulic pressure generating device so as not to significantly affect the size of the driving apparatus.
More precisely, the above-mentioned driving apparatus may be constructed such that the electric motor, gear train, and the differential device are housed in a case for the driving apparatus, and the case for the driving apparatus is provided with an intermediate wall that separates at least an electric motor chamber, in which the electric motor is housed, from a gear chamber that houses the gear train with the hydraulic pressure generating device embedded in the intermediate wall.
In the construction according to an embodiment of the first exemplary aspect of the invention, disposing the hydraulic pressure generating device does not require any additional special member, which contributes to a simplified structure and a resultant reduced cost, in addition to a reduced installation space requirement.
It is also effective if a valve body having a circuit formed therein for distributing a pressure oil generated by the hydraulic pressure generating device into the electric motor chamber and the gear chamber is provided in a fixed condition in the intermediate wall to cover the hydraulic pressure generating device.
In the construction according to another embodiment the first exemplary aspect of the invention, the path between the hydraulic pressure generating device and the valve body becomes the shortest, which allows power loss of the hydraulic pressure generating device to be reduced.
In case when the valve body that has the circuit formed therein for distributing the oil pressure generated by the hydraulic pressure generating device into the electric motor chamber and the gear chamber is provided, it would be even more effective if such a valve body has the hydraulic pressure generating device built therein and is embedded in the intermediate wall.
In the construction according to yet another embodiment the first exemplary aspect of the invention, the path between the hydraulic pressure generating device and the valve body becomes the shortest, which allows power loss of the hydraulic pressure generating device to be reduced. Moreover, the valve body as well as the hydraulic pressure generating device is embedded in the intermediate wall, which eliminates the need of any additional special member for disposing the valve body and the hydraulic pressure generating device, which in turn contributes to a simplified structure and a resultant reduced cost, in addition to a reduced installation space requirement.
In case the driving apparatus is further provided with an engine, it would be effective if the gear train is disposed between the engine and the electric motor in a positional relationship in an axial direction.
In the construction according to still another embodiment the first exemplary aspect of the invention, each of the foregoing effects can be achieved in a hybrid driving apparatus.
In case the driving apparatus is further provided with a planetary gear set that mutually and operatively couples the engine, the electric motor, and the counter drive gear, it would be possible to provide a structure, in which an isolating wall is provided that defines a planetary chamber that accommodates the planetary gear set in cooperation with the intermediate wall.
In the construction according to another embodiment of the first exemplary aspect of the invention, each of the foregoing effects can be achieved in a hybrid driving apparatus, in which the engine and the electric motor are operatively coupled to the gear train through the planetary gear set to allow differential movement.
In addition, in case the driving apparatus is further provided with a braking device that stops rotation of the electric motor through the supply of pressure oil generated by the hydraulic pressure generating device, it would be effective if such a braking device is disposed in the isolating wall.
In the construction according to yet another embodiment of the first exemplary aspect of the invention, the oil passage used for engaging and releasing the brake device that requires the supply of a particularly high hydraulic pressure and supply response, among other points to which hydraulic pressure is supplied, can be routed along the shortest path via the intermediate wall and the isolating wall, which results in reduced power loss of the hydraulic pressure generating device from an overall viewpoint of the driving apparatus.
The driving apparatus according to the invention includes the electric motor and the gear train, that operatively couples the electric motor to a wheel, housed in the case for the driving apparatus. The case for the driving apparatus is provided with the intermediate wall that separates at least the electric motor chamber, in which the electric motor is housed, from the gear chamber that houses the gear train, and the isolating wall that defines a separate chamber in either the electric motor chamber or the gear chamber in cooperation with the intermediate wall, and is characterized in that the hydraulic pressure generating device is disposed in the intermediate wall and the braking device that stops rotation of the electric motor through the supply of oil pressure generated by the hydraulic pressure generating device is disposed in the isolating wall.
In the construction according to a second exemplary aspect of the invention, disposing the hydraulic pressure generating device does not require any additional special member, which contributes to a simplified structure and a resultant reduced cost, in addition to a reduced installation space requirement. Moreover, the oil passage used for engaging and releasing the brake device that requires the supply of a particularly high hydraulic pressure and supply response among other points to which hydraulic pressure is supplied can be routed along the shortest path via the intermediate wall and the isolating wall, which results in power loss of the hydraulic pressure generating device being reduced from an overall viewpoint of the driving apparatus.
In this case also, it would be effective if the gear train is disposed between an engine, if the driving apparatus is provided therewith, and the electric motor in the positional relationship in the axial direction.
In the construction according to an embodiment of the second exemplary aspect of the invention, each of the foregoing effects can be achieved in a hybrid driving apparatus.
Likewise, in case the driving apparatus is further provided with the engine, electric motor, and a planetary gear set that mutually and operatively couples one of the gears in a gear train that operatively couples the electric motor to a wheel, it would be effective if the planetary gear set is housed in the separate chamber.
In the construction according to another embodiment of the second exemplary aspect of the invention, each of the foregoing effects can be achieved in a hybrid driving apparatus, in which the engine and the electric motor are operatively coupled to the gear train through the planetary gear set to allow differential movement.